Wavelet and multifractal estimation of the intermittent photic stimulation response in the electroencephalogram of patients with dyscirculatory encephalopathy

The task is to elucidate quantitative characteristics in electroencephalographic (EEG) patterns giving the possibility to estimate the disruptions of the functional state of the central nervous system caused by dyscirculatory encephalopathy of different severity. For solving the task the background and reactive EEG patterns are analyzed by the continuous wavelet transform and the wavelet-transform modulus maxima methods. The EEG responses to intermittent photic stimulation are used as reactive patterns. There are no statistical differences between the width of the singularity spectra of background and reactive patterns for all the subjects. Therefore, the degree of multifractality determined by this parameter does not change considerably during the photic stimulation. By contrast, the coefficients of photic driving and holding and the energy increase times gained in EEG patterns of patients with dyscirculatory encephalopathy differ significantly from the parameters determined for the healthy subjects. The reactive patterns have been demonstrated to have the different photic driving of beta, theta and alpha ranges for the patients of various groups. Frequencies of the theta range are reproduced mainly in the EEG patterns of patients with hypertension disease and with vertebrobasilar insufficiency. The maximal photic driving reaction of the beta range is noticed in the group with the vegetovascular dystonia. Frequencies of the alpha range are predominantly reproduced by the group with hypertension disease. The study demonstrates the opportunity to estimate quantitatively the dynamics of changes in energy characteristics of EEG patterns for various groups of patients having cerebrovascular disturbances. The results can be applied for an appropriate choice of treatment for such patients with the regard for their photic driving reactions.